1. Field of the Invention
This invention relates to gas turbine combustors and more specifically to combustion systems that are interconnected by crossfire tube assemblies for ignition purposes.
2. Description of Related Art
In a typical industrial gas turbine engine, a plurality of combustors are arranged in a generally annular array about the engine. Each combustor receives pressurized air from the engine compressor and has a means of fuel injection. Given an ignition source, the proper temperature levels of both the fuel and air, as well as sufficient mixing of the fluids, combustion will occur. The resulting hot gases leave the combustors and enter a turbine, which drives a generator to generate electricity. Due to the cost and control complexity of ignition systems, typically only one or two combustors have an ignition source. Therefore, in order to initiate combustion in all combustors, it has become standard practice to interconnect the combustors with crossfire tube assemblies. Crossfire tubes are configured to transfer a flame between adjacent combustors during the initial start-up period. Although a crossfire tube assembly is advantageous by eliminating additional ignition sources, it has operational issues including cooling, excessive wear, and oxidation, each of which can lead to premature replacement.
A crossfire tube of the prior art is shown in FIG. 1. In this embodiment, a hollow inner tube 10 is telescopically received within a hollow outer tube 11. The ends of the telescope-like assembly 12 and 13 are received within adjacent combustors 14 and 15 and the assembly serves to transfer a flame between combustors 14 and 15. Inner tube 10 is clipped to plate 21 at groove 19 while outer tube 11 is clipped to plate 20 at groove 18. While inner tube 10 and outer tube 11 serve to adequately transfer a flame between combustors 14 and 15, ends 12 and 13 have been known to experience significant wear due to frictional rub contact with cross fire receptacles 16 and 17. Furthermore, wear has been known to occur in crossfire clip grooves 18 and 19 due to rubbing between the crossfire tube clip and inner tube 10 and outer tube 11. Crossfire tubes of the prior art are typically manufactured from relatively soft material, typically a stainless steel, while crossfire tube clips are often manufactured from a harder material. While some wear is expected to the crossfire tubes, since they are subject to some movement, engine vibrations, and are considered consumable items, it is desirable to further extend their life to reduce operating costs associated with premature replacement.